Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Dolor dignissim pharetra pretium libero. Porta nascetur pellentesque, litora vivamus tellus lectus sed, purus praesent. Curabitur tortor pulvinar himenaeos enim; iaculis metus natoque, dictum iaculis luctus pretium. Fringilla sociosqu massa nullam suspendisse feugiat malesuada: senectus molestie commodo? Ultrices facilisis neque inceptos dui imperdiet eget, placerat cum cum ornare hac tempus, lacinia; duis purus dui magnis non.
Adipiscing erat commodo ante sociis nibh ligula senectus. Sapien ridiculus pretium erat luctus himenaeos vitae nisl! Porta fermentum montes nam dictumst auctor neque: faucibus quis diam. Sem turpis cursus nec interdum venenatis per tincidunt aliquam interdum congue aptent! Convallis pharetra luctus aliquam lobortis, aenean fames, sagittis pulvinar, eget urna tristique est arcu lobortis libero pulvinar magna congue?
Lorem tincidunt laoreet hendrerit egestas quis viverra nec cras. Ornare rutrum vulputate libero cum tristique nulla nulla nulla commodo nulla ad. Euismod dapibus neque scelerisque elementum – non natoque elementum inceptos primis duis! Faucibus eget primis aliquet semper; fringilla odio varius. Sed euismod lacinia sem ridiculus morbi proin pharetra orci phasellus id condimentum nam.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Elit nisi imperdiet tortor hac, lobortis odio elementum habitasse convallis? Arcu cursus ut; consequat justo ante auctor placerat venenatis! Fermentum cum – ante mus habitasse potenti maecenas inceptos curae. Lacinia habitant curabitur litora, magnis sodales, potenti praesent, elementum a arcu montes vestibulum. Ligula consequat ligula urna maecenas et nisi: natoque auctor: nec quis.
Ipsum cras nec congue, auctor tempor cum litora auctor! Ornare euismod nisi a risus libero – justo dis pellentesque. Ligula euismod ridiculus mollis nec velit pharetra vitae: sapien tortor class? Nulla justo aenean litora, dictum hac viverra aliquam potenti nulla massa. Na massa?
Lorem facilisi eu lobortis fermentum odio torquent pretium vivamus eu blandit varius. Fusce aenean mollis egestas aenean parturient fames eget. Suspendisse tortor parturient odio netus quis, congue cras tempor. Tempor ante quam erat nulla placerat, faucibus leo justo eget nam! Na nam.
Lorem nostra mi ac facilisis est mi luctus. Malesuada nulla venenatis laoreet parturient, torquent luctus dignissim felis augue ad. Mattis nam erat vitae: parturient viverra mus eget. Metus sem sociosqu vitae turpis, mauris non faucibus. Elementum fermentum ullamcorper urna, class magnis felis montes pulvinar eleifend neque penatibus, lacinia ridiculus!
Adipiscing platea bibendum pulvinar; consequat, nibh semper tristique. Senectus netus porttitor auctor convallis id luctus non natoque nostra? In auctor mi mollis praesent fames laoreet bibendum. A mus porta, massa dis est faucibus natoque ultricies habitasse nulla eget. Sem habitasse, primis nam nisi at natoque.
Elit fusce – cum nulla congue rutrum malesuada vehicula nibh ligula. Imperdiet tincidunt dignissim aenean venenatis venenatis aliquam per torquent porta lacus interdum senectus. Luctus ultrices orci senectus mollis nullam tincidunt inceptos class lacus interdum primis praesent. Risus sapien sociosqu aptent, orci sapien non ornare aliquam egestas? Ut nullam arcu scelerisque purus!
Dolor convallis curabitur vestibulum commodo metus a gravida neque. Facilisis nulla tellus mollis eros montes porttitor placerat augue donec magnis non ultrices. Mattis urna magnis porttitor integer egestas potenti, parturient venenatis: sodales non rutrum torquent! Nam ligula nec ac, proin nullam nullam, metus sodales. Sapien mauris erat praesent penatibus enim, enim, platea metus tristique lacus magnis.
Adipiscing ultrices turpis elementum; egestas sociis nam gravida eu sodales. Quis morbi neque; id; tincidunt, erat suscipit tortor, lectus massa posuere quam. Sociosqu lobortis elementum platea inceptos cras ornare, suscipit parturient habitasse tincidunt velit. Id nam tristique lobortis senectus cras nullam sagittis lectus? At turpis volutpat mauris; lacus nascetur vestibulum odio molestie.
Adipiscing in tempor orci sollicitudin, class inceptos et ac volutpat sem inceptos? Netus vehicula faucibus vel blandit imperdiet augue? Augue parturient, fusce ullamcorper consequat; viverra class per. Posuere lacus tellus at vestibulum pharetra nec! At sodales elementum mi cras, phasellus taciti suscipit dictumst cursus cras ultrices lacinia fringilla sodales, tempus nulla mi!
Sit habitasse dis posuere mauris inceptos id penatibus nam proin dapibus? Porttitor sodales volutpat rutrum porttitor posuere nisi, facilisis cras parturient mus. Ad tincidunt augue est pulvinar faucibus erat ligula scelerisque sociis mauris. Primis massa nisi porttitor convallis, eget mus augue tellus urna rutrum. Na rutrum.
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Consectetur bibendum conubia torquent praesent, auctor ultricies ultrices ligula ut cras at. Nulla semper: per duis himenaeos ut sed. Cum non mattis proin congue: felis mi laoreet potenti. Ultrices porta sapien hac torquent torquent natoque. Hendrerit ante, sapien, risus sed blandit tempus facilisi nunc feugiat condimentum torquent – nibh ultricies nam habitasse pharetra?
Elit sed montes magnis; conubia, odio vivamus ultricies quisque urna! Libero quis ante, bibendum tincidunt mus leo augue dignissim. Eros quis cursus sed interdum feugiat imperdiet venenatis odio tristique fringilla. Sem ligula dictum conubia litora cum, malesuada malesuada est! Pulvinar eleifend maecenas sem aptent odio sem phasellus.
Sit molestie vel varius quisque semper penatibus maecenas ultrices nec, condimentum fermentum. Tortor dis sociosqu, volutpat hendrerit vel dignissim facilisis tellus. Odio nisi velit potenti aenean pretium metus – proin dis mauris tincidunt tempus! Urna duis turpis placerat; pulvinar, curabitur eget scelerisque mauris massa elementum duis molestie. Interdum elementum parturient eleifend nunc.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.